Joinder of porcelain enameled products



July 2, 1946. w. w. HIGGINS 2,403,079

JOINDER OF PORCELAIN ENAMELED PRODUCTS Filed April so, 1942 .Il l Il I IIIHHHI` IIIIIIl'I" IIIIHIIIIII Waldo WH/gmf INVE f OR.

BY: www

AT TZYEY Patented July 2,

PATENT OFFICE.

2,403,079 JOINDER F PORCELAIN ENAMELED PRODUCTS what w. umm, wnaemn nu. wa., am

to A. 0. Smith Corporation, Milwaukee y.corporation of New York Appunti@ April so. mz. serial Nc. 441,201

, s claims. (cl. 154er) This invention relates to the joinder of porcelain enameled products.

The principal object of the invention is to provide a novel method of interfusing ceramic enamel coatings on articles.

an article of two or more parts bonded together by a)fused ceramic enamel material free from the entrapment of air or gases.

In accordance with the invention the parts to be joined are first enameled to present a, comparatively small initial area of contact when assembled under pressure contact, assembled and heated to a temperature substantially below the firing temperature of the enamel to soften the L obtaining reactions in the coatings such as occur upon reflring. Preferably, the temperature em- 4 ployed will be from one hundred to two hundred latter and graduallyincrease the area of contact, effecting bonding ofA the enamel coatings.

In carrying out the invention it is preferable to have the enamel crowned in thickness at the center on the flat surfaces to be joined so as to` provide an initial contact in a restricted central area which progressivelyexpands outward as the enamel coatings soften under heat and pressure until the required area of Jolnder is obtained.

Furthermore, the enamel coatings should be of substantial thickness to provide the best bond therebetween. t

'I'he preferred method of carrying out the invention is illustrated in' the accompanying drawing, in which:

Figurevl is a transverse section through two enameled metal parts to be joined, shown in pressure contact ready for the interfusion of the coatlgs; and

Fig. 2 is a similar view of the parts after the 35 joinder is completed.

The parts I and 2 to be joinedl arevof metal and may be of any desired shape depending upon the article being fabricated. The parts l and 2 have their respective opposed adjacent faces 3 40 and 4 complementary, preferably flat, and the shape of the parts should be symmetrical so that their expansion and contraction under temperature changes will not disrupt the enamel bond.

they are assembled with the crowned enamel coatings in'initial contact over a restricted area near the center of the surfaces being joined. 'I'he parts are then pressed together as by a weight i .5 or by other suitable pressure applying means, Another object` of the invention is tolprovide preferablyi under a pressure of about one-half pound per square inch'of surface. The actual pressure employed may be substantially 'greater and maybe varied depending upon the type and thickness of enamel and the temperature employed for interfusing the same.

The parts, thus held together under Pressure,

are then heated to a temperature sufficient to substantially soften the enamel coatings without decomposing any of the constituents and without degrees below the firing temperature of the last enamel coat. Where a firing temperature in ex' cess of 1600 F. is employed,` a heating to about 1450 F. for about 35 minutes under the pressure conditions described is sumcient to obtain a good bonding of the enamel coats together.v 'The length after the partsfhave cooled below the criticall temperature of the enamel so that the latter has become set. y n

The invention provides an interfusion of the enamel coatings free from flaws at the Joinder. The parts are bonded together with a fluid tight Joint therebetween having a tensile strength of the order of at least three thousand pounds per square inch.

The invention may be employed to join a seriesl of partstogether asin the manufacture of high tension electrical.- insulating bushings andthe like, as set forth in applicants copending application, Serial No. 441,199, filed on even date here- The faces 3. and I are first enameled with sevwith, or it may be employed in the manufacture eral successive coats of a. hard ceramic enamel with a firing temperature around 16o0 F. The last coat of enamel should be of a composition and should be applied under conditions which of various other products vsuch as in the jolnder of ceramic lined parts subject to corrosion and in which the linings are interfused over the joint.

Various embodiments of the invention may be avoid surface defects. This final coat is preferemplcyed within the scope of the accompanying ably brushed away at the outer edges prior to firing so as to obtain a crowned surface with the l enamel thicker at the center than at the edges as illustrated in exaggerated form in Fig. l.

The invention is claimed as follows:

1. The method of `ioining metal members by a fused ceramic material bonded to their opposed After the parts are enameled as above described adjacent surfaces, comm-umg. @am the 1d i with attendant progressive increasein the area of contact therebetween to thereby interiuse said coatings substantially free from gas bubbles at 2. The method of interfusing ceramic enamel coatings on opposed adjacent surfaces of metal members, comprising centrally crowning the coatings to be joined, assembling the members with thevcoatings in contactand applying pressureand heat simultaneously to soften and inter,-

. fuse the coatings.

3. The method of interfusingv ceramic enamel coatings on opposed adjacent surfaces of metal members, comprising assembling said members with the enamel coatings in restricted initial contact, and applying heat and pressure to soften the coatings and progressively increase the area of contact therebetween until the coatings are interfusedv and bonded together over a substantial area.

4. The method of interfusing ceramic enamel coatings on opposed adjacent surfaces oi' metal members, comprising assembling said members with the enamel coatings in restricted initial contact, and applying heat and pressure to soften the coatings and progressively increase the area of contact therebetween until the coatings are Ainterfused and bonded together over a substantial'area, said heating being to asuilciently low temperature to prevent reactions inthe coating attendant upon reflring thereof.

5. In ceramic enameling the flat surface of a member preparatory to interfusing the same with another, the. steps of applying and firing successive coats of ceramic enamel thereto to obtain .the required thickness of enamel, and applying and firing a coat of ceramic enamel on only a.

vportion of the surface of the member to` provide a crownin the surface for facilitating the inter-v fusion of the enamel surfaces.

6. The method of interfusing ceramic enamel coatings on complementaryV surfaces of metal members, comprising applying and firing an ad-V ditional coat of ceramic enamel on only a portion of the enameled surface of the member to provide a crown in the surface for facilitating the interfusion of the enamel surfaces,'and applying pressure and heat simultaneously to soften and interfuse the coatings. WALDO W. HIGGINS. 

